The present invention relates generally to information handling systems including computer systems and related devices which store data in volatile and nonvolatile memory. and, more particularly, to an uninterruptible power.supply system and method for providing a backup power supply for such systems.
Information handling systems such as computers are used in all areas of business and personal use and require reliable power to operate effectively. At times, the public utility power source, may not be sufficient. If the utility power source fails, important operations may not be performed and valuable electronic data may become lost or corrupted.
To cope with such power source failure, an uninterruptible power supply (UPS) may be used. UPS systems contain a battery and are connected between an information handling system and the power source. In the event of a power failure or power dropping to an unacceptable voltage level, the battery may be used to provide battery power to operate the system. Since the cost of a UPS system is proportional to the length of available backup time, typical UPS systems are limited to a few minutes of backup capacity, i.e., so that a user has enough time to save his or her work and power down the information handling system in an orderly manner.
UPS systems may be advantageously employed for even commonplace information handling tasks, such as those performed with a desktop computer. For example, in a conventional personal computing environment, the use of write back caches, wherein updated data intended for the disk is temporarily stored in volatile RAM to improve performance, increases the chance that data will be lost in the event of a power failure occurs. It would, therefore, be desirable to provide a UPS system that is cost effective for use in everyday information handling tasks.
One shortfall of typical UPS systems is that a user must be present to manually shut down the system is power is interrupted, particularly where a computer is running unattended, for example, where the computer is performing a monitoring application or other continuous application, or, where the user is simply away from the computer. To overcome this shortcoming, various prior art schemes for automatically saving the system state and shutting down the system are known in the art.
For example, in U.S. Pat. No. 5,603,038 there is disclosed a method for automatic restoration of user options after a power loss. The reference discloses four computer states: a normal operating state, a standby state, a suspend state, and an off state. In one embodiment, waking a computer for a user-specified event that would not be lost if power is disrupted is disclosed. This is accomplished with a preprogrammed microcontroller interfaced to the system and powered by an auxiliary power supply. Another embodiment discloses saving the state of the computer system to the fixed disk storage device prior to turning the power supply off.
U.S. Pat. No. 5,021,983 discloses a suspend/resume apparatus and method for reducing power consumption in a battery powered computer. Suspending operation of a computer is performed by storing the state of the computer in RAM and disconnecting power to all other components in the computer. When resumption of operation is commanded, power is restored to all components and the computer state is restored from RAM, allowing operations to continue from the same point as when they were suspended.
U.S. Pat. No. 5,765,001 discloses a computer system which is operative to change from a normal operating state to a suspend state when a power supply thereof detects that an external source is no longer providing power to said power supply at a predetermined level. One embodiment discloses a power management circuit connected to an internal power source wherein the power management circuit causes the computer system to change to the suspend state wherein the entire state of the system is safely saved to a non-volatile storage device.
U.S. Pat. No. 5,530,877 discloses an apparatus for providing continuity of operation in a computer. One embodiment discloses a save process start detector which manages and determines the timing at which the system state is to be saved. The save process is triggered by turning off a power switch, a low battery state, an instruction from the system user, and the like. Once the determination to save the system status is. made, the system state is output to an external nonvolatile memory.
U.S. Pat. No. 5,598,567 discloses an apparatus for controlling a power supply in a computer,system by introducing delays before activation and deactivation of power. In one embodiment, a computer system can properly operate even when the power supply is reactivated immediately after its deactivation or when the power supply is deactivated during the execution of a resume process.
However, there does not exist in the art a UPS system and method for preventing the system from resuming from a suspended state until after a predetermined period of time has elapsed, after which time it is reasonably safe to assume that the external power supply is stable. Furthermore, there does not exist in the art a UPS system and method for preventing the system from resuming until the backup power supply has sufficient capacity to maintain power long enough to.perform another system restoration should the external AC power fail again.
In one aspect, the present invention provides a power management system and method for an information handling system comprising a power storage device for supplying power to the information handling system and a detector for detecting the power level of the power storage device, wherein the power management system prevents the information handling system from resuming operation until the detector detects that the power level of the power storage device is sufficient to permit the informnation handling system to perform a data saving function.
In another aspect, the present invention provides a power management system and method for an information handling system comprising a power storage device for supplying power to the information handling system and a detector for detecting the power level of the power storage device, wherein the power management system prevents the information handling system from resuming operation until the detector detects that an external power supply has been stable for a predetermined period of time.
In another aspect, the present invention provides an information handling system and method comprising a power storage device for supplying power to the information handling system and a detector for detecting the power level of the power storage device, wherein the information handling system is prevented from resuming operation until the detector detects that the power level of the power storage device is sufficient to permit the info pration handling system to perform a data saving function.
In yet another aspect, the present invention provides an information handling system and method comprising a power storage device for supplying power to the information handling system and a detector for detecting the power level of the power storage device, wherein the information handling system is prevented from resuming operation until the detector detects that an external power supply has been stable for a predeterm period of time.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given. above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.